the replication of DNA. This technique is known as the dideoxy chain-termination method or the Sanger method, and is used to determine the order of nucleotides in DNA. The 3′-end of nascent messenger RNA is the site of post-transcriptional polyadenylation, which attaches a chain of 50 to 250 adenosine residues to produce mature messenger RNA. This chain helps in determining how long the messenger RNA lasts in the cell, influencing how much protein is produced from it. The 3′-flanking region is a region of DNA that is not copied into the mature mRNA, but which is present adjacent to 3′-end of the gene. It was originally thought that the 3′-flanking DNA was not transcribed at all, but it was discovered to be transcribed into RNA and quickly removed during processing of the primary transcript to form the mature mRNA. The 3′-flanking region often contains sequences that affect the formation of the 3′-end of the message. It may also contain enhancers or other sites to which proteins may bind. The 3′-untranslated region (3′-UTR) is a region of the DNA which is transcribed into mRNA and becomes the 3′-end of the message, but which does not contain protein coding sequence. Everything between the stop codon and the polyA tail is considered to be 3′-untranslated. The 3′-untranslated region may affect the translation efficiency of the mRNA or the stability of the mRNA. It also has sequences which are required for the addition of the poly(A) tail to the message, including the hexanucleotide AAUAAA. See also Sense (molecular biology) Further reading External links A Molecular Biology Glossary DNA Molecular genetics RNA